The acute effects of time-of-day-dependent high fat feeding on whole body metabolic flexibility in mice.

BACKGROUND: Both circadian disruption and timing of feeding have important roles in the development of metabolic disease. Despite growing acceptance that the timing of food consumption has long-term impact on metabolic homeostasis, little is known regarding the immediate influence on whole body metabolism, or the mechanisms involved. We aimed to examine the acute effects of time-of-day-dependent high fat feeding on whole body substrate metabolism and metabolic plasticity, and to determine the potential contribution of the adipocyte circadian clock. METHODS: Mice were fed a regimen of 4-h meal at the beginning and end of the dark (waking) cycle, separated by 4 h of fasting. Daily experimental conditions consisted of either an early very high fat or high fat (EVHF or EHF, 60 or 45% kcals from fat, respectively) or late (LVHF or LHF) meal, paired with a low fat (LF, 10% kcals from fat) meal. Metabolic parameters, glucose tolerance, body fat composition and weight were assessed. To determine the role of the adipocyte circadian clock, an aP2-CLOCK mutant (ACM) mouse model was used. RESULTS: Mice in the EVHF or EHF groups showed a 13.2 or 8.84 higher percentage of caloric intake from fat and had a 0.013 or 0.026 lower daily average respiratory exchange ratio, respectively, compared with mice eating the opposite feeding regime. Changes in glucose tolerance, body fat composition and weight were not significant at the end of the 9-day restricted feeding period. ACM mice did not exhibit different metabolic responses to the feeding regimes compared with wild-type littermates. Circadian clock disruption did not influence the short-term response to timed feeding. CONCLUSIONS: Both the total fat composition of diet and the timing of fat intake may differentially mediate the effect of timed feeding on substrate metabolism, but may not induce acute changes in metabolic flexibility.

Quantitative analysis of light-phase restricted feeding reveals metabolic dyssynchrony in mice.

BACKGROUND: Considerable evidence suggests that the time of day at which calories are consumed markedly impacts body weight gain and adiposity. However, a precise quantification of energy balance parameters during controlled animal studies enforcing time-of-day-restricted feeding is currently lacking in the absence of direct human interaction. OBJECTIVE: The purpose of the present study was therefore to quantify the effects of restricted feeding during the light (sleep)-phase in a fully-automated, computer-controlled comprehensive laboratory animal monitoring system (CLAMS) designed to modulate food access in a time-of-day-dependent manner. Energy balance, gene expression (within metabolically relevant tissues), humoral factors and body weight were assessed. RESULTS: We report that relative to mice fed only during the dark (active)-phase, light (sleep)-phase fed mice: (1) consume a large meal upon initiation of food availability; (2) consume greater total calories per day; (3) exhibit a higher respiratory exchange ratio (indicative of decreased reliance on lipid/fatty acid oxidation); (4) exhibit tissue-specific alterations in the phases and amplitudes of circadian clock and metabolic genes in metabolically active tissues (greatest phase differences observed in the liver and diminution of amplitudes in epididymal fat, gastrocnemius muscle and heart); (5) exhibit diminished amplitude in humoral factor diurnal variations (for example, corticosterone); and (6) exhibit greater weight gain within 9 days of restricted feeding. CONCLUSIONS: Collectively, these data suggest that weight gain following light (sleep)-phase restricted feeding is associated with significant alterations in energy balance, as well as dyssynchrony between metabolically active organs.

Time-of-day-dependent dietary fat consumption influences multiple cardiometabolic syndrome parameters in mice.

BACKGROUND: Excess caloric intake is strongly associated with the development of increased adiposity, glucose intolerance, insulin resistance, dyslipidemia, and hyperleptinemia (that is the cardiometabolic syndrome). Research efforts have focused attention primarily on the quality (that is nutritional content) and/or quantity of ingested calories as potential causes for diet-induced pathology. Despite growing acceptance that biological rhythms profoundly influence energy homeostasis, little is known regarding how the timing of nutrient ingestion influences development of common metabolic diseases. OBJECTIVE: To test the hypothesis that the time of day at which dietary fat is consumed significantly influences multiple cardiometabolic syndrome parameters. RESULTS: We report that mice fed either low- or high-fat diets in a contiguous manner during the 12 h awake/active period adjust both food intake and energy expenditure appropriately, such that metabolic parameters are maintained within a normal physiologic range. In contrast, fluctuation in dietary composition during the active period (as occurs in human beings) markedly influences whole body metabolic homeostasis. Mice fed a high-fat meal at the beginning of the active period retain metabolic flexibility in response to dietary challenges later in the active period (as revealed by indirect calorimetry). Conversely, consumption of high-fat meal at the end of the active phase leads to increased weight gain, adiposity, glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and hyperleptinemia (that is cardiometabolic syndrome) in mice. The latter perturbations in energy/metabolic homeostasis are independent of daily total or fat-derived calories. CONCLUSIONS: The time of day at which carbohydrate versus fat is consumed markedly influences multiple cardiometabolic syndrome parameters.

20p12.3 microdeletion predisposes to Wolff-Parkinson-White syndrome with variable neurocognitive deficits.

BACKGROUND: Wolff-Parkinson-White syndrome (WPW) is a bypass re-entrant tachycardia that results from an abnormal connection between the atria and ventricles. Mutations in PRKAG2 have been described in patients with familial WPW syndrome and hypertrophic cardiomyopathy. Based on the role of bone morphogenetic protein (BMP) signalling in the development of annulus fibrosus in mice, it has been proposed that BMP signalling through the type 1a receptor and other downstream components may play a role in pre-excitation. METHODS AND RESULTS: Using the array comparative genomic hybridisation (CGH), we identified five individuals with non-recurrent deletions of 20p12.3. Four of these individuals had WPW syndrome with variable dysmorphisms and neurocognitive delay. With the exception of one maternally inherited deletion, all occurred de novo, and the smallest of these harboured a single gene, BMP2. In two individuals with additional features of Alagille syndrome, deletion of both JAG1 and BMP2 were identified. Deletion of this region has not been described as a copy number variant in the Database of Genomic Variants and has not been identified in 13 321 individuals from other cohort examined by array CGH in our laboratory. CONCLUSIONS: Our findings demonstrate a novel genomic disorder characterised by deletion of BMP2 with variable cognitive deficits and dysmorphic features and show that individuals bearing microdeletions in 20p12.3 often present with WPW syndrome.

Circadian rhythms in the development of obesity: potential role for the circadian clock within the adipocyte.

Obesity is one of the most profound public health problems today, and simplistic explanations based on excessive nutritional consumption or lack of physical activity are inadequate to account for this dramatic and literal growth in our world population. Recent reports have suggested that disruptions in sleep patterns, often linked to our '24-h' lifestyle, are associated with increased body fat and altered metabolism, although the cause-effect relationship for these associations has yet to be elucidated. Abnormal sleep/wake patterns likely alter intracellular circadian clocks, which are molecular mechanisms that enable the cell/tissue/organism to anticipate diurnal variations in its environment. The environment may include circulating levels of nutrients (e.g. glucose, fatty acids and triglycerides) and various hormones (e.g. insulin, glucocorticoids). As such, alterations in this molecular mechanism, in particular within the adipocyte, likely induce metabolic changes that may potentiate disrupted metabolism, adipose accumulation and/or obesity. Although diurnal variations in adipokines and adipose tissue metabolism have been observed, little is known regarding the molecular mechanisms that influence these events.

Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations.

Reactive Fe(III) minerals can influence methane (CH4 ) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total). Iron reduction, methanogenesis, CH4 oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4 -stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history.

Positional genomic analysis identifies the beta(2)-adrenergic receptor gene as a susceptibility locus for human hypertension.

BACKGROUND: -After genome-wide linkage analyses of blood pressure levels, we resequenced 5 positional candidate genes in a linkage region on chromosome 5 and genotyped selected variants in several family samples from Rochester, Minn. METHODS AND RESULTS: In a sample of 55 pedigrees containing >/=1 sibling-pair(s) discordant for systolic blood pressure, polymorphisms within the beta(2)-adrenergic receptor gene (Arg16Gly, P=0.009) and the glutathione peroxidase 3 gene (-302G-->A, P=0.037; -623A-->C, P=0.013) were significantly related to blood pressure levels. In a second sample of 298 nuclear families (n=1283 individuals), the Arg16Gly polymorphism was significantly associated with diastolic blood pressure in family-based analyses (P=0.016) and with both diastolic (P=0.009) and mean arterial blood pressure (P=0.038) in analyses of the parental generation only. Neither polymorphism in the glutathione peroxidase 3 gene was associated with blood pressure levels in this sample. An additional 291 families (n=1240 individuals) were added to the nuclear family sample, and the Gln27Glu polymorphism in the beta(2)-adrenergic receptor gene was significantly associated with both systolic (P=0.034) and mean arterial blood pressure (P=0.035) in the parental generation of the combined 589 families. The frequencies of both the Gly16 and Glu27 alleles were higher in hypertensives than in normotensives (0.649 versus 0.604 and 0.490 versus 0.429, respectively), and the odds ratio for the occurrence of hypertension was 1.80 (95% confidence interval, 1.08 to 3.00; P=0. 023) for the Glu27 allele. CONCLUSIONS: The results of this study provide support for further detailed investigations of the mechanistic pathways by which variations in the beta(2)-adrenergic receptor gene may influence blood pressure levels.

High-throughput multiplex SNP genotyping with MALDI-TOF mass spectrometry: practice, problems and promise.

Single nucleotide polymorphisms (SNPs) are currently being identified and mapped at a remarkable pace, providing a rich genetic resource with vast potential for disease gene discovery, pharmacogenetics, and understanding the origins of modern humans. High-throughput, cost effective genotyping methods are essential in order to make the most advantageous and immediate use of these SNP data. We have incorporated the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) in our laboratory as a tool for differentiating genotypes based on the mass of the variant DNA sequence, and have utilized this method for production scale SNP genotyping. We have combined a 4 microl PCR amplification reaction using 3 ng of genomic DNA with a secondary enzymatic reaction (mini-sequencing) containing oligonucleotide primers that anneal immediately upstream of the polymorphic site, dideoxynucleotides, and a thermostable polymerase used to extend the PCR product by a single base pair. Mass spectrometry (MS) analysis of mini-sequencing reactions was performed using a MALDI-TOF instrument (Voyager-DE, Perseptive Biosystems, Framingham, MA). We performed both single and multiplex PCR and mini-sequencing reactions, and genotyped seven different variant sites in a random sample of 989 individuals. Genotypes generated with MS methods were compared with genotypes produced using a 5' exonuclease fluorescence-based assay (Taqman, Applied Biosystems, Foster City, CA) and a gel-based genotyping protocol. Because multiple polymorphisms can be detected in a single reaction, the MS technique provides a cost-effective and efficient method for high-throughput genotyping.

Association and linkage analysis of the alpha-adducin gene and blood pressure.

In Milan hypertensive rats, a variant in the alpha-adducin gene has been shown to account for approximately 50% of the interindividual variation in blood pressure levels between these animals and their normotensive counterparts. Additional studies have suggested that a polymorphism within exon 10 of the human alpha-adducin gene (Gly-460-Trp) may be associated with hypertension and salt sensitivity. On the basis of these observations, we investigated variation within or near the human alpha-adducin gene for linkage and association with a locus influencing blood pressure levels in 281 nuclear families (774 siblings aged 5 to 37 years; 380 parents aged 26 to 57 years), selected from the white population of Rochester, Minnesota, without regard to health. Sib pair linkage analyses (n = 852 sibling pairs) using a dinucleotide repeat marker (D4S43) that maps approximately 660 kb from the alpha-adducin gene provided no evidence of linkage between this marker locus and a locus influencing systolic, diastolic, or mean blood pressure levels. Allele frequencies for the Gly-460-Trp polymorphism were similar to those reported in other white populations (Gly = 0.812, Trp = 0.188); however, this polymorphism was not associated with any measure of blood pressure level in either parents or siblings. Therefore, variation within the alpha-adducin gene does not appear to have a major influence on measures of blood pressure in white families from Rochester, Minnesota.

Genomics, genes, and environmental interaction: the role of exercise.

Regular exercise has been shown to improve control of lipid abnormalities, diabetes mellitus, hypertension, and obesity, with the greatest benefits realized by sedentary individuals who begin to exercise. Responses to exercise interventions are often highly variable among individuals, however, and research has indicated that response to exercise may be mediated in large part by variation in genes. As we strive to unravel the complex etiology of diseases like obesity, diabetes, and cardiovascular disease through the use of molecular and genetic tools now available, understanding the interaction and influence of environmental factors, such as exercise, on gene expression and function has taken on increasing importance. This review briefly summarizes strategies presently being used to elucidate genes and genetic effects that may be mediated or influenced by exercise and serves to illustrate the importance of considering the effect of exercise when investigating genes related to health or other physiological outcomes.

Insulin improves functional and metabolic recovery of reperfused working rat heart.

BACKGROUND: Glucose, insulin, and potassium solution improves left ventricular function in refractory pump failure. Direct effects of insulin on the heart cannot be determined in vivo. We hypothesized that insulin has a direct positive inotropic effect on the reperfused heart. METHODS: Isolated working rat hearts were perfused with buffer containing glucose (5 mmol/L) plus oleate (1.2 mmol/L). Hearts were subjected to 15 minutes of ischemia and reperfused with or without insulin (100 microU/mL) for 40 minutes. Epinephrine (1 micromol/L) was added for the last 20 minutes. RESULTS: Hearts recovered 51.1% of preischemic cardiac power in the absence and 76.4% in the presence of insulin (p < 0.05). Whereas oleate oxidation remained unchanged, glucose uptake and oxidation increased during reperfusion with epinephrine (p < 0.01). This increase was significantly greater when hearts were reperfused in the presence of insulin (p < 0.01). Insulin also prevented an epinephrine-induced glycogen breakdown during reperfusion (p < 0.05). CONCLUSIONS: Insulin has a direct positive inotropic effect on postischemic rat heart. This effect is additive to epinephrine and occurs without delay. Increased rates of glucose oxidation and net glycogen synthesis are more protracted.

Caltrac versus calorimeter determination of 24-h energy expenditure in female children and adolescents.

The purpose of this study was to determine the validity of the Caltrac accelerometer for estimating 24-h energy expenditure (EE) in children and adolescents. EE for 40 girls (13.0 +/- 1.8 yr) was assessed for 24 h via indirect calorimetry in whole-room calorimeters. EE and activity level were estimated concurrently by two Caltrac accelerometers placed on the subjects at each hip. Significant correlations (P < 0.001) resulted between Caltrac estimates and calorimeter values for 24-h total EE (TEE, r = 0.80), sedentary daily EE (SDEE, r = 0.84), and waking EE (WEE, r = 0.85). Nonetheless, the Caltrac significantly (P < 0.001) underestimated EE in all experimental conditions (TEE: -13.3 +/- 8.6%; SDEE: -6.8 +/- 7.3%; WEE: -30.4 +/- 8.5%). A significant multiple correlation between calorimeter values and a combination of Caltrac activity counts and body weight (R = 0.86, P < 0.001) suggested these variables could be useful for daily EE estimation. Additional analyses indicated that as EE increased, the absolute difference between Caltrac and calorimeter values also increased. The significant correlations between Caltrac and calorimeter values suggest the Caltrac may be useful for assessing daily caloric expenditure for groups of children.

Ethnicity affects aerobic fitness in US adolescent girls.

The purpose of this investigation was to determine whether aerobic fitness (VO2max) differed between black (N = 40) and white (N = 53) adolescent girls who were similar in age (13.5 yr) and percent body fat (24.6%). Expired gases were collected continuously while each girl performed a standard Bruce protocol to volitional exhaustion on a motorized treadmill (TM). Heart rates (HR) were measured during the exercise testing via telemetry. Fat-free mass (FFM) was estimated with total body electrical conductivity (TOBEC). Average (+/- SD) maximum HR (black = 194 +/- 7; white = 198 +/- 8) and respiratory exchange ratios (black = 1.17 +/- 0.08; white = 1.22 +/- 0.09) did not differ between subject groups. Aerobic fitness was significantly lower (P < 0.01) lower in black versus white girls when VO2max was expressed relative to body weight (31.8 +/- 5.8 vs 38.5 +/- 6.8 ml.kg(-1).min(-1)) and body weight raised to the 0.67 power (120.9 +/- 19.5 vs 138.5 +/- 20.7 ml.kg(-0.67).min-1). Treadmill time to exhaustion was significantly less (P < 0.01) in the black (8.49 +/- 1.30 min) versus white (9.41 +/- 1.60) subjects. Also, black subjects demonstrated less ability to utilize O2 during maximal exercise at a given FFM. This suggests the black girls' FFM contained a smaller percentage of skeletal muscle mass that could be utilized during treadmill exercise. It is possible that lower aerobic fitness values seen in the black girls are related to a combination of anatomical, physiological and/or behavioral factors.

Genetic factors in exercise adoption, adherence and obesity.

Physical activity and exercise play critical roles in energy balance. While many interventions targeted at increasing physical activity have demonstrated efficacy in promoting weight loss or maintenance in the short term, long term adherence to such programmes is not frequently observed. Numerous factors have been examined for their ability to predict and/or influence physical activity and exercise adherence. Although physical activity has been demonstrated to have a strong genetic component in both animals and humans, few studies have examined the association between genetic variation and exercise adherence. In this review, we provide a detailed overview of the non-genetic and genetic predictors of physical activity and adherence to exercise. In addition, we report the results of analysis of 26 single nucleotide polymorphisms in six candidate genes examined for association to exercise adherence, duration, intensity and total exercise dose in young adults from the Training Interventions and Genetics of Exercise Response (TIGER) Study. Based on both animal and human research, neural signalling and pleasure/reward systems in the brain may drive in large part the propensity to be physically active and to adhere to an exercise programme. Adherence/compliance research in other fields may inform future investigation of the genetics of exercise adherence.

VAMP8/endobrevin is overexpressed in hyperreactive human platelets: suggested role for platelet microRNA.

BACKGROUND: Variation in platelet reactivity contributes to disorders of hemostasis and thrombosis, but the molecular mechanisms are not well understood. OBJECTIVES: To discover associations between interindividual platelet variability and the responsible platelet genes, and to begin to define the molecular mechanisms altering platelet gene expression. SUBJECTS/METHODS: Two hundred and eighty-eight healthy subjects were phenotyped for platelet responsiveness. Platelet RNA from subjects demonstrating hyperreactivity (n=18) and hyporeactivity (n=11) was used to screen the human transcriptome. RESULTS: Distinctly different mRNA profiles were observed between subjects with differing platelet reactivity. Increased levels of mRNA for VAMP8/endobrevin, a critical v-SNARE involved in platelet granule secretion, were associated with platelet hyperreactivity (Q=0.0275). Validation studies of microarray results showed 4.8-fold higher mean VAMP8 mRNA levels in hyperreactive than hyporeactive platelets (P=0.0023). VAMP8 protein levels varied 13-fold among platelets from these normal subjects, and were 2.5-fold higher in hyperreactive platelets (P=0.05). Among our cohort of 288 subjects, a VAMP8 single-nucleotide polymorphism (rs1010) was associated with platelet reactivity in an age-dependent manner (P<0.003). MicroRNA-96 was predicted to bind to the 3'-untranslated regionof VAMP8 mRNA and was detected in platelets. Overexpression of microRNA-96 in VAMP8-expressing cell lines caused a dose-dependent decrease in VAMP8 protein and mRNA, suggesting a role in VAMP8 mRNA degradation. CONCLUSIONS: These findings support a role for VAMP8/endobrevin in the heterogeneity of platelet reactivity, and suggest a role for microRNA-96 in the regulation of VAMP8 expression.

The role of cell-specific circadian clocks in metabolism and disease.

Biological rhythms are an integral component of essentially all aspects of life. These rhythms are controlled in part by circadian clocks, transcriptionally based mechanisms that synchronize the organism to its changing environment. The central circadian clock is located within the suprachiasmatic nucleus of the brain, while peripheral clocks are located within virtually all cells outside of the suprachiasmatic nucleus. Although our understanding of central clock structure and function is well advanced, the role of peripheral clocks in whole body energy metabolism is just beginning to be elucidated. Both central and peripheral circadian clocks likely regulate many physiological functions, including insulin sensitivity, endocrine regulation, energy homeostasis, satiety signalling, cellular proliferation and cardiovascular function. Widely varying phenotypes have been reported following global genetic disruption of the clock mechanism in mice, with phenotype dependent on both the clock component targeted and genetic background. The inconsistency in phenotypes associated with clock disruption may be due, in part, to cell-specific effects of the circadian clocks. To address this question, many laboratories have begun generating animal models of cell type-specific clock disruption. In this review, we summarize the existing literature on tissue-specific models of circadian clock disruption and provide a focus for future research in this area.

Circadian biology and sleep: missing links in obesity and metabolism?

This supplement highlights key talks presented at the Pennington Symposium. The collected papers provide a state of the art review of circadian biology at the basic and clinical levels in the context of nutrition, obesity and sleep medicine. Investigators from multiple disciplines attempted to translate new information concerning molecular mechanisms into practical clinical applications, as well as foster new research hypotheses and directions to this exciting field of science and medicine. Furthermore, we hope to spark the interest and attention of the next generation of scientists who will tackle the questions presented by the changing interface between technology, lifestyle and biological rhythms.

Cyclooxygenase polymorphisms and risk of cardiovascular events: the Atherosclerosis Risk in Communities (ARIC) study.

Cyclooxygenase-derived prostaglandins modulate cardiovascular disease risk. We genotyped 2212 Atherosclerosis Risk in Communities study participants (1,023 incident coronary heart disease (CHD) cases; 270 incident ischemic stroke cases; 919 non-cases) with available DNA for polymorphisms in PTGS1 and PTGS2. Using a case-cohort design, associations between genotype and CHD or stroke risk were evaluated using proportional hazards regression. In Caucasians, the reduced function PTGS1 -1006A variant allele was significantly more common among stroke cases compared to non-cases (18.2 versus 10.6%, P=0.027). In African Americans, the reduced function PTGS2 -765C variant allele was significantly more common in stroke cases (61.4 versus 49.4%, P=0.032). No significant relationships with CHD risk were observed. However, aspirin utilization appeared to modify the relationship between the PTGS2 G-765C polymorphism and CHD risk (interaction P=0.072). These findings suggest that genetic variation in PTGS1 and PTGS2 may be important risk factors for the development of cardiovascular disease events. Confirmation in independent populations is necessary.

Gene-environment interaction and the GNB3 gene in the Atherosclerosis Risk in Communities study.

OBJECTIVE: The purpose of this study was to investigate the interaction between the G-protein beta-3 (GNB3) 825C>T polymorphism and physical activity in relation to prevalent obesity and hypertension. RESEARCH METHODS AND PROCEDURES: The GNB3 825C>T genotype was measured in a sample of 14,716 African Americans (AAs) and whites from the Atherosclerosis Risk in Communities (ARIC) study, and logistic regression was used to test for genetic effects and gene-environment interactions. RESULTS: The GNB3 825C>T variant was not independently associated with prevalent obesity or hypertension in either AA or whites. However, we observed a significant interaction (P<0.001) between this variant and physical activity in predicting obesity status in AAs. In AAs who were active, each 825T allele was associated with a 20% lower prevalence of obesity (odds ratio (OR)=0.80, 95% confidence interval (CI)=0.689-0.937, P=0.005), whereas each 825T allele was associated with a 23% greater prevalence of obesity for low-active individuals (OR=1.23, 95% CI=1.06-1.44, P=0.008). We also found a significant interaction between the GNB3 825C>T polymorphism, obesity status and physical activity in predicting hypertension in the AA subjects. AA homozygotes for the 825T allele who were both obese and had a low activity level were 2.7 times more likely to be hypertensive, compared to non-obese, active 825C homozygotes (OR=2.71, 95% CI=1.19-6.17, P<0.02). DISCUSSION: Our findings suggest that the variation within the GNB3 gene may interact with physical activity level to influence obesity status and, together with obesity and physical activity, the GNB3 825C>T variant may influence hypertension prevalence in AAs.

Genetic variation and decreased risk for obesity in the Atherosclerosis Risk in Communities Study.

AIM: To investigate the effects of variation in the leptin [LEP (19A>G)] and melanocortin-4 receptor [MC4R (V103I)] genes on obesity-related traits in 13 405 African-American (AA) and white participants from the Atherosclerosis Risk in Communities (ARIC) Study. METHODS: We tested the association between the single-locus and multilocus genotypes and obesity-related measures [body mass index (BMI), body weight (BW), waist-hip ratio, waist circumference and leptin levels], adjusted for age, physical activity level, smoking status, diabetic status, prevalence of coronary heart disease, hypertension, stroke or transient ischaemic attack. RESULTS: AA and white female carriers of the MC4R I103 allele exhibited significantly lower BW than non-carriers of this allele (p < 0.05 and p < 0.01 respectively). AA female carriers of both the LEP A19 allele and the MC4R I103 allele were 63% [odds ratio (OR) = 0.37, 95% confidence interval (CI) (0.18-0.78)] less likely to be obese, and white female carriers of the same two alleles were 46% [OR = 0.54, 95% CI (0.32-0.91)] less likely to be obese, than non-carriers of the variant alleles. Female carriers of both the LEP A19 and MC4R I103 alleles had significantly lower BW (p < 0.05), BMI (p < 0.05) and plasma leptin (p < 0.01) than the non-carriers of both the alleles. Carriers of the two variant alleles had lower BMI over the 9-year course of the ARIC study and significantly lower weight gain from age 25 years. No significant joint effect of these two variants was observed in males. CONCLUSION: These results suggest that variation within the LEP and MC4R genes is associated with reduced risk for obesity in females.